Converting a text box value into a character array?

I'm using a .NET Forms Application, and I have a text box that I want to copy the value of to an array of char's. I'll be the first to admit, I'm quite inexperienced with .NET, and honestly, C/C++ in general.

The trouble is, I can't seem to do it the other way around. Am I just missing something? I suppose I should wait until tomorrow to be working on a non-negative amount of sleep, but when I come across a problem, my mind refuses to let it rest.

Please, someone point out whatever it is that my mind refuses to comprehend.